Given the function:

$\displaystyle s(t)=\sin2\pi*t$

My book says: $\displaystyle s'(t)=2\pi*\cos2\pi*t$

I'm pretty sure this is a utilization of the chain rule, but I don't really understand it, can someone clear it up for me?

(ps, sorry I could not get it to show up any clearer...)